Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 4: Topology and Symmetry-Protected Materials
O 4.4: Vortrag
Montag, 5. September 2022, 11:15–11:30, H6
Simultaneous AFM and STM measurements of native point Defects in the topological insulator Bi2Se3 — •Christoph Setescak, Alexander Liebig, Adrian Weindl, and Franz J. Giessibl — Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany
The main properties of topological insulators (TIs) can be derived from the fact that their band structure is "twisted" compared to normal insulators, leading to the creation of gapless states at the surface. To observe these states and make them viable for application in novel technologies it is crucial that the materials delicate electronic structure is not disturbed by defects. So far, experimental characterization of the native point defects relies on scanning tunneling microscopy (STM) and accompanying density functional theory [1]. Here, we present simultaneous atomic force microscopy (AFM) and STM measurements of surface and subsurface defects in Bi2Se3. We find not only rarely-observed single Se surface vacancies, but also larger defects that are composed of multiple surface vacancies. The AFM channel furthermore allows us to determine the relative relaxation of surface atoms in proximity of subsurface defects and to determine the polarity of surface defects by means of Kelvin probe force spectroscopy. This is especially valuable as surface Se vacancies contribute to unwanted charge doping of the TI. [1] J. Dai et al., PRL 117, 106401 (2016)